The objective of this study is a definition of a relationship of bile acids and/or their derivatives to the etiology of cancer of the large bowel. Specifically, the project will continue the investigation of dietary effects on the nature and quantities of bile acids in the hepatobiliary circulation of the rat and the effect of gonadal hormones on the composition of rat bile. A coupled system of gas chromatograph-mass spectrometer-computer will be utilized with high pressure liquid chromatography to quantitate and identify bile acids. Enzymatic assays will augment these studies to provide quantitation.